Process of producing an alkali-metal silicate-clay adhesive



106. C MP HI N MM MW a- COATING R PLASTIC; W a EXANHN 8 Patented Febr18,1 941 UNITED STATES PATENT OFFICE SILICATE-CLAY ADHESIVE Ernest R. Boiler, Cleveland Heights, Ohio, as-

signor to E. I. du Pont de Nemours & Company, Wilmington, Del., a. corporation of Delaware No Drawing. Application May 26, 1939,

Serial No. 275,803

6 Claims. (Cl. 134-2332) This invention relates to processes for making clay with dilute silicate adhesives particularly a stable suspension of china clay in silicates: adapted for use in corrugated board machines. LR

dis

\\i moons: 0F raonnomc. AN ALKALI-MET- i tion according to which the chifia clay is I have found that satisfactory, stable silicate E-E d i water by means of agitation an clay adhesives may be prepared withdiiute silithe china clay dispersion is adaedfo'and adc at eand small amounts of cla by first dispersing mixed with asili-cate solutionn. 4. the clay inmr and then a mixing the clay diss Clay is frequently added to sodium silicate adpers on With the sodium silicate. Silicate flake; hesives to increase their viscosity and to improve smthus prepared according to my invention are their adhesive characteristics so that they will ally adap for e in the manufacture of 10 be better adapted for application to paper as on laminated paper a d d ru a d pap r 10 laminated paper board and corrugated board board. The clay has a g eat y diminished mach1nes ency to settle from the solutions despite their When clay is used with a relatively concentratrelatively w c i y and the adhesives do not ed sodium silicate solution, say 42.5 B., a fairly show the pron unc d t n e cy for the aration stable suspension is obtained by simple mixing, 0f clay which has heretofore made adhesives of 15 But when an attempt is made to suspend clay in this type remely diflicult to use.

more dilute sodium silicate solutions unstable e agitation y means o which p ion)! suspensions are obtained from which the clay clay in er s secu ed y be effected y y settles out very rapidly. suitable apparatus. The mixture of clay and w The rapid settling of clay from dilute silicate y be Worked in an e e r ner mill, 8 001- 20 solutions makes dilute silicate-clay adhesives difii- 9 B1111, ar device for effecting p cult to transport and use. Clay settles in tank 51011- It is ient simply to use a highp cars and pipe lines and also forms a sediment in mixer- 1 paper board machines. In addition to the me- The suspension 0f 3 in Water may be aided chanical difllculties caused by the separation of P the use f dispersin r defi cuts 25, J

clay, there is the further problem caused by the If desired 1310118 8 ot n cessary. It is frevariation in adhesive composition. The separaquently fund convenient, instance, o mtion of clay from the adhesive during use requires P Small amount of ilic te of soda-to aid in frequent readjustment of the paper board equipforming the suspension. ather such alkaline det, floeeulating agents such as trisodium phosphate 30 In the Thickens Patent 1,377,739 it was prog mav likewise be usa'-- e 1 posed to make more stable silicate-clay adhesives 79119115 sodium Silioate solutions may be used by prolonged agitation of the clay with a con-cenaccordmg to my invention. In general, it is P trated silicate in which the clay forms a relatively ferred that the te have n sioz/NazO weight stable dispersion. After a stable dispersion ratio of about 3.25 but this may be varied ac- 35 was obtained, it was proposed that water then be (Bedding 1 e Prac ice known to the trade. added to bring the adhesive to the desired con- The silicate solutions in w ic clay is suscentration. This procedure was proposed mostly pended according to my invention may also vary for use with compositions containing a very large Wldely as to their Sp fic gravity and it will genamount of clay. Even with compositions cony e desired to use solutions havingaviscosity 40 taining a large amount of clay these processes corresponding o t of a 3.25 ratio silicate soluaccording to which clay is agitated with a silicate having a av y of from afiut 30 to 41 B. solution do not produce entirely satisfactory ad- More ly, th advantages 0! my inven'- hesives, tion will be most apparent with solutions with a 45 It has also been proposed to prepare various vlscosity corresponding to t t of a .2 rat1osi1i- 45 coating compositions and even adhesives which te s luti n avi a ravity n t su stan a ly are moderately stable by reason of their containr er han about 40 B. ing only a relatively small amount of sodium silie amount of c a a used w ll depend cate. These are usually thick and relatively visupon the c er of the adhesive desired in cous and they contain large amounts f filler accordance with the practice known to the art. 50 such as clay or starch or inert ingredients. With In ral, e advantages of my i n i n are these coating compositions containing only relabest obtained with silicate-clay adhesives which tively small amounts of sodium silicate the art contain between about five to fifteen per cent by has not been faced with the problem of making a. weight gf ghina clay. MW

as stable mixture of a relatively small amount of Processes 13? the pr paration of stable silieateclay adhesives according to this invention must be carefully carried out according to the tea-chings of my invention if satisfactory adhesives are to be produced. The clay must be suspended 5 with or without a defiocculating agent in a measured amount of water. The amount of water must be taken into account in considering the final strength of the silicate solution above mentioned. The clay dispersion after preparation must be gldedfiasilicatasolutimiihilm It is to be observed that it is not satisfactory to add the silicate solution to the clay suspension for when this is done a very thick and sometimes almost solid mass results as the first additions of silicate are made, and it is difllcult to finish the preparation of the adhesive.

Small amounts of starch or of other iner may be present in the silicate-clay adhes ves 0 this invention but it is desirable that no more than about five per cent of such an inert be present.

My invention may be better understood by reference to the following illustrative examples.

Example I The amount of water, cla and 425 B. so-

hesive composition containing fifteen parts of clay and eighty-two parts of 300 B. sodium silicate solution was determine 0 e W8. er

was added one per cent of the total 42.5" 136. sililers the blades being about three inches long.

The propellers were driven at 1800 R. P. M. The mixing was effected in a 110-gallon steel drum.

The suspension of china clay in water was added to the 425 B. silicate solution, 3.25 ratio,

and the mixture was stirred to insure homogeneity.

The silicate-clay adhesive so produced showed only a little settling and no sediment was deposited upon standing.

Example II The amount of china clay, water, and 425 B. silicate solution required finally to produce an adhesive composition containing ten per cent clay and ninety per cent 395 B. silicate was determined and the required amount of clay was added to the water.

The mixture of clay with water was passed through an attrition mill after which there was obtained a suspension so thick that it would barely fiow. The mill employed was of the type known as an edge runner paint mill.

The suspension of clay in water was then added to the required amount of 42.5 B. silicate. The

0 mixture was made homogeneous by stirring. The

siligate solution used had an SiOz/NazO ratio of 3.2 'Ifie silicate-clay adhesive produced showed no sedimentation upon standing and there was only a little settling. When a column of the adhesive was permitted to stand for twenty-four hours there wasa clear, supernatant layer somewhat less than ten per cent of the total height of the column. a

While I have shown a number of illustrative examples it will be understood that those skilled in the art may suspend china clay in water and then admix with a silicate solution to make dilute silicate-clay adhesives in various ways without 15 departing from the spirit of my invention,

qium silicate required fina y o produce an ad- I claim:

1. In a process for the production of an alkali metal silicate-clay adhesive, the step comprising agitating china clay in an amount equivalent to about five to fifteen per cent by weight of the adhesive with water to make a suspension and then adding the suspension to a silicate solution, the silicate solution being used in such an amount that the viscosity of the silicate solution comprising the adhesive would correspond to the viscosity of a 3.25 ratio silicate solution having a gravity not substantially greater than about 40 B.

2. In a process for the production of an alkali metal silicate-china clay adhesive which in addition to the china clay contains no more than about five per cent of inerts the balance being substantially silicate solution, the step comprising agitating china clay in an amount equivalent to about five to fifteen per cent by weight of the adhesive with water to make a suspension and then adding the suspension to a silicate solution, the silicate solution being used in such an amount that the viscosity of the silicate solution comprising the adhesive would correspond to the viscosity of a 3.25 ratio silicate solution having a gravity not substantially greater than about 38 3. An alkali metal silicate-china clay adhesive comprising from about five to fifteen per cent of china clay and no more than about five per cent of additional inerts, the balance of the composition being a silicate solution with a viscosity corresponding to that of a 3.25 ratio silicate solution having a gravity of about 30 to 41 B., the adhesive being relatively stable by reason of the china clay first being suspended in water and then added to the silicate solution.

4. In a process for the production of an alkali metal silicate-clay adhesive, the steps comprising agitating china clay in an amount equivalent to about five to fifteen per cent by weight of the adhesive with water to make a suspension and then adding the clay suspension to a silicate solution, the silicate solution being used in such an amount that the viscosity of the silicate solution comprising the adhesive would correspond to the viscosity of a 3.25 ratio silicate having a gravity from about 30 to 41 Baum.

5. In a process for the production of an alkali metal silicate-clay adhesive, the steps comprising agitating china clay in an amount equivalent to about five to fifteen per cent by weight of the adhesive with water and a defiocculating agent to make a suspension and then adding the clay suspension to a silicate solution, the silicate solution being used in such an amount that the viscosity of the silicate solution comprising the adhesive would correspond to the viscosity of a 3.25 ratio silicate having a gravity from about 30 to 41 Baum.

6. In a process for the production of an alkali metal silicate-clay adhesive, the steps comprising agitating china clay in an amount equivalent to about five to fifteen per cent by weight of the adhesive with water and a small amount of trisodium phosphate to make a suspension and then adding the clay suspension to a silicate solution, the silicate solution being used in such an amount that the viscosity of the silicate solution comprising the adhesive would correspond to the viscosity of a 3.25 ratio silicate having a gravity from about 30 to 41 Baum.

ERNEST R. BQLLER. 

